- “Each one of these souls is finite and precious. And I'm close. Close to saving them all.”— The Librarian
First-Light-Weaves-Living-Song, more commonly known as The Librarian, was a Forerunner who served as the Lifeshaper (leader of the Lifeworker caste). She sought to document and index all sentient beings of the Milky Way and protect them from being absorbed into the Flood by sending them to the shelter of the Ark. Of all the races she indexed, she deeply respected Humanity, whom she viewed as "special" among all of the sentient life she had seen. She felt that saving them was well-worth dying for.
Post Human-Forerunner war
Soon after the Human-Forerunner War, the Librarian learned of the Flood and its potential threat to the galaxy. After successfully pleading the council to preserve as many humans as possible due to their possible knowledge of a cure for the Flood, she focused on studying humanity and aiding the Didact with the creation of his shield worlds. She soon noticed the rapid development of humans and therefore hid their progress from the council, the Master Builder, and, most importantly, the Didact.
After having lost every political battle for his shield world, the Didact was forced into exile. The Librarian, already planning for the future, hid him and his cryptum on Erde-Tyrene, also known as Earth. Shortly thereafter, she came to believe that she had discovered the galaxy from which the Flood originated. She acquired a ship and crew to explore it. They discovered a world of primitive Forerunners that her race far surpassed in technology. A native bit her: the bite seemed to transfer information—like a universal form of communication. The inhabitant then escorted the Librarian to a biological Domain. Having obtained a moss-like plant that seemed to hold yet more information from the same planet, the Librarian collected more data. Upon returning home, she continued indexing the galaxy's species because the Flood had by then returned.
The Greater Ark was the location of most of the Librarian's species and index samples, but during the end of the Forerunner-Flood war, she had to move most of her species to the Halo guarding this ark. But things did not go as planned. As the Flood assaulted the Greater Ark, the Ur-Didact composed most of the human population from his warship, Mantle's Approach.
The Librarian followed the Ur-Didact to the core of Requiem. She gained entrance to his chambers, wounded him with a Binary Rifle, and imprisoned him inside his Cryptum. She left with the knowledge that the Domain would undo what the Gravemind had done to him. Before leaving Requiem, The Librarian left an imprint of herself behind.
After leaving her husband and Requiem, the Librarian returned to Earth to make sure that her lifeworkers had gathered enough humans to ensure the survival of the human race. She transferred her rank of Lifeshaper to one of her most trusted lifeworkers and then orders them to leave her behind and escape to Installation 00.
The Librarian bought the IsoDidact and her lifeworkers some time by sending a fake message to send the Flood to Earth instead of to the Lesser Ark. This tactic left her with the knowledge that the Domain was created by the Precursors, and that firing the Halos will destroy the Domain and all other Precursor artifacts and leave the Ur-Didact to eternally sit and meditate on his anger.
The Librarian would perish on Earth during the firing of the Halo Array.
Imprint on Requiem
In 2557, the Librarian appears before John-117 during the First Battle of Requiem. She explains to the Reclaimer her plans to ensure that mankind will inherit the Mantle of Responsibility, mankind's ancient history with the Forerunners and the motivations of the Didact, and his plans for the Composer. She then tells John that when she indexed humanity for re-population, she had placed seeds that would lead to the creation of the Spartans, their Mjolnir armor, and even John's Ancilla Cortana. She claims that he's "the culmination of a thousand lifetimes of planning." But before she could elaborate, the Didact appeared, demanding that she relinquish her dialogue with the human. With little time, the Librarian reveals that she had also placed genes within the Master Chief's DNA that contained many gifts that included an immunity to the effects of the Composer that had to be unlocked. She quickly enables the immunity once she confirmed that the Didact couldn't be stopped without it.
Six months after the Didact's defeat, Jul 'Mdama's Covenant maintained a presence on Requiem because they believed that the Librarian was hiding on the planet and sought to release her in the hope that she would grant them powers and technologies beyond imagination. Later, Dr. Catherine Halsey managed to activate the device that the Sangheili had been trying to activate. Upon succeeding, she rushed into the shrine and conversed with the Librarian, who, to advance humanity, showed her the Janus Key, which revealed every piece of Forerunner technology in the galaxy if brought to the Absolute Record. Halsey asked why she was being entrusted with such an important object, and the Librarian answered that while Requiem would soon cease to exist, the Key and what it contains must not be lost. As soon as the Librarian handed Halsey the Key and released her, Jul grabbed one half while Halsey hurled the other to Gabriel Thorne. The Librarian's statement about Requiem's time being at an end concretized as Jul 'Mdama, in possession of one half of the Key, set Requiem to collide with its sun, which ended in the destruction of the shield world and therefore of the Librarian's imprint inside the shrine.
- The Librarian's glyph is an emblem in Halo 3's Multiplayer.
- The Librarian was mentioned in Halo 3 in the Terminals. In conversations, she is known as "L."
- On one of the Terminals in Halo 3, you can see the symbol of the Librarian.
- The Librarian referred to the part of Earth she resided on as "Eden" - a reference to the garden of Eden in Abrahamic religions.
- The Proto-Gravemind was originally called "The Librarian."
- According to 343 Guilty Spark, the Librarian was the only one who could "temper" the Didact's rage.
- The ending of Halo: Primordium strongly suggests that the Librarian may be alive, contrary to what her husband said.
- The Librarian is the second Forerunner whose face has been depicted in the Halo series (the first being the Ur-Didact). Other Forerunners have been seen but they have all been wearing Combat Skins.
- The Librarian manipulated the DNA of reseeded humans to guide them towards the development of the skills and technology they would require to uphold the Mantle. Such technologies include augmentation (Spartan II's augmentations), advanced combat skins (Mjolnir Powered Assault Armor), and AI creation (AI). These manipulations would eventually culminate in the creation of one specific human who would be play a central role in Mankind's reclamation of the Mantle.
- The Forerunner records of her transmissions utilize translation software so advanced that it incorporates idioms from the reader's own experience. Such words as "Eden," and "Librarian" are not transliterations of their Forerunner counterparts, but close approximations in the English language that consider the cultural and linguistic idiosyncrasies inherent in the language itself. The Librarian's true name is First-Light-Weaves-Living-Song and Librarian is the English approximation of her name.
- Halo: The Flood (Mentioned only)
- Halo 3
- Halo: Cryptum (First appearance)
- Halo: Primordium (Mentioned only)
- Halo: Silentium
- Halo: Combat Evolved Anniversary
- Terminals (Mentioned only)
- Halo 4